Method and apparatus for supporting one-to-one sidelink communication in a wireless communication system

ABSTRACT

A method and apparatus are disclosed from the perspective of an initiating UE (User Equipment) for establishing a one-to-one sidelink communication with a target UE. In one embodiment, the method includes transmitting a first PC5 signaling used for establishing the one-to-one sidelink communication, wherein the first PC5 signaling includes an identity of the target UE and an identity of a V2X (Vehicle-to-Everything) service.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present Application claims priority to and is a continuation of U.S.application Ser. No. 16/703,265, filed on Dec. 4, 2019, entitled “METHODAND APPARATUS FOR SUPPORTING ONE-TO-ONE SIDELINK COMMUNICATION IN AWIRELESS COMMUNICATION SYSTEM”, the entire disclosure of which isincorporated herein in its entirety by reference. U.S. application Ser.No. 16/703,265 claims the benefit of U.S. Provisional Patent ApplicationSer. No. 62/784,631 filed on Dec. 24, 2018, the entire disclosure ofwhich is incorporated herein in its entirety by reference.

FIELD

This disclosure generally relates to wireless communication networks,and more particularly, to a method and apparatus for handling mobilityof a UE with one-to-one sidelink communication in a wirelesscommunication system.

BACKGROUND

With the rapid rise in demand for communication of large amounts of datato and from mobile communication devices, traditional mobile voicecommunication networks are evolving into networks that communicate withInternet Protocol (IP) data packets. Such IP data packet communicationcan provide users of mobile communication devices with voice over IP,multimedia, multicast and on-demand communication services.

An exemplary network structure is an Evolved Universal Terrestrial RadioAccess Network (E-UTRAN). The E-UTRAN system can provide high datathroughput in order to realize the above-noted voice over IP andmultimedia services. A new radio technology for the next generation(e.g., 5G) is currently being discussed by the 3GPP standardsorganization. Accordingly, changes to the current body of 3GPP standardare currently being submitted and considered to evolve and finalize the3GPP standard.

SUMMARY

A method and apparatus are disclosed from the perspective of aninitiating UE (User Equipment) for establishing a one-to-one sidelinkcommunication with a target UE. In one embodiment, the method includestransmitting a first PC5 signaling used for establishing the one-to-onesidelink communication, wherein the first PC5 signaling includes anidentity of the target UE and an identity of a V2X(Vehicle-to-Everything) service.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 shows a diagram of a wireless communication system according toone exemplary embodiment.

FIG. 2 is a block diagram of a transmitter system (also known as accessnetwork) and a receiver system (also known as user equipment or UE)according to one exemplary embodiment.

FIG. 3 is a functional block diagram of a communication system accordingto one exemplary embodiment.

FIG. 4 is a functional block diagram of the program code of FIG. 3according to one exemplary embodiment.

FIG. 5 is a reproduction of Figure 6.11.3.1-1 of 3GPP TR 23.786 V1.0.0.

FIG. 6 is a reproduction of Figure 6.11.3.1-2 of 3GPP TR 23.786 V1.0.0.

FIG. 7 is a reproduction of Figure 6.11.3.3-1 of 3GPP TR 23.786 V1.0.0.

FIG. 8 is a reproduction of Figure 6.19.2.1.2-1 of 3GPP TR 23.786V1.0.0.

FIG. 9 is a reproduction of Figure 6.1.3.1a-1 of 3GPP TS 36.321 V15.3.0.

FIG. 10 is a reproduction of Figure 6.1.3.1a-2 of 3GPP TS 36.321V15.3.0.

FIG. 11 is a diagram according to one exemplary embodiment.

FIG. 12 is a diagram according to one exemplary embodiment.

FIG. 13 is a diagram according to one exemplary embodiment.

FIG. 14 is a diagram according to one exemplary embodiment.

FIGS. 15A-15D are diagrams according to one exemplary embodiment.

FIG. 16 is a flow chart according to one exemplary embodiment.

FIG. 17 is a flow chart according to one exemplary embodiment.

FIG. 18 is a diagram according to one exemplary embodiment.

FIG. 19 is a diagram according to one exemplary embodiment.

FIG. 20 is a flow chart according to one exemplary embodiment.

FIG. 21 is a flow chart according to one exemplary embodiment.

DETAILED DESCRIPTION

The exemplary wireless communication systems and devices described belowemploy a wireless communication system, supporting a broadcast service.Wireless communication systems are widely deployed to provide varioustypes of communication such as voice, data, and so on. These systems maybe based on code division multiple access (CDMA), time division multipleaccess (TDMA), orthogonal frequency division multiple access (OFDMA),3GPP LTE (Long Term Evolution) wireless access, 3GPP LTE-A orLTE-Advanced (Long Term Evolution Advanced), 3GPP2 UMB (Ultra MobileBroadband), WiMax, 3GPP NR (New Radio), or some other modulationtechniques.

In particular, the exemplary wireless communication systems devicesdescribed below may be designed to support one or more standards such asthe standard offered by a consortium named “3rd Generation PartnershipProject” referred to herein as 3GPP, including: RAN2 #104 Chairman'sNote; 3GPP TR 23.786 V1.0.0, “Study on architecture enhancements for EPSand 5G System to support advanced V2X services”; and TS 36.321 V15.3.0,“Evolved Universal Terrestrial Radio Access (E-UTRA); Medium AccessControl (MAC) protocol specification”. The standards and documentslisted above are hereby expressly incorporated by reference in theirentirety.

FIG. 1 shows a multiple access wireless communication system accordingto one embodiment of the invention. An access network 100 (AN) includesmultiple antenna groups, one including 104 and 106, another including108 and 110, and an additional including 112 and 114. In FIG. 1, onlytwo antennas are shown for each antenna group, however, more or fewerantennas may be utilized for each antenna group. Access terminal 116(AT) is in communication with antennas 112 and 114, where antennas 112and 114 transmit information to access terminal 116 over forward link120 and receive information from access terminal 116 over reverse link118. Access terminal (AT) 122 is in communication with antennas 106 and108, where antennas 106 and 108 transmit information to access terminal(AT) 122 over forward link 126 and receive information from accessterminal (AT) 122 over reverse link 124. In a FDD system, communicationlinks 118, 120, 124 and 126 may use different frequency forcommunication. For example, forward link 120 may use a differentfrequency then that used by reverse link 118.

Each group of antennas and/or the area in which they are designed tocommunicate is often referred to as a sector of the access network. Inthe embodiment, antenna groups each are designed to communicate toaccess terminals in a sector of the areas covered by access network 100.

In communication over forward links 120 and 126, the transmittingantennas of access network 100 may utilize beamforming in order toimprove the signal-to-noise ratio of forward links for the differentaccess terminals 116 and 122. Also, an access network using beamformingto transmit to access terminals scattered randomly through its coveragecauses less interference to access terminals in neighboring cells thanan access network transmitting through a single antenna to all itsaccess terminals.

An access network (AN) may be a fixed station or base station used forcommunicating with the terminals and may also be referred to as anaccess point, a Node B, a base station, an enhanced base station, anevolved Node B (eNB), or some other terminology. An access terminal (AT)may also be called user equipment (UE), a wireless communication device,terminal, access terminal or some other terminology.

FIG. 2 is a simplified block diagram of an embodiment of a transmittersystem 210 (also known as the access network) and a receiver system 250(also known as access terminal (AT) or user equipment (UE)) in a MIMOsystem 200. At the transmitter system 210, traffic data for a number ofdata streams is provided from a data source 212 to a transmit (TX) dataprocessor 214.

In one embodiment, each data stream is transmitted over a respectivetransmit antenna. TX data processor 214 formats, codes, and interleavesthe traffic data for each data stream based on a particular codingscheme selected for that data stream to provide coded data.

The coded data for each data stream may be multiplexed with pilot datausing OFDM techniques. The pilot data is typically a known data patternthat is processed in a known manner and may be used at the receiversystem to estimate the channel response. The multiplexed pilot and codeddata for each data stream is then modulated (i.e., symbol mapped) basedon a particular modulation scheme (e.g., BPSK, QPSK, M-PSK, or M-QAM)selected for that data stream to provide modulation symbols. The datarate, coding, and modulation for each data stream may be determined byinstructions performed by processor 230.

The modulation symbols for all data streams are then provided to a TXMIMO processor 220, which may further process the modulation symbols(e.g., for OFDM). TX MIMO processor 220 then provides N_(T) modulationsymbol streams to N_(T) transmitters (TMTR) 222 a through 222 t. Incertain embodiments, TX MIMO processor 220 applies beamforming weightsto the symbols of the data streams and to the antenna from which thesymbol is being transmitted.

Each transmitter 222 receives and processes a respective symbol streamto provide one or more analog signals, and further conditions (e.g.,amplifies, filters, and upconverts) the analog signals to provide amodulated signal suitable for transmission over the MIMO channel. N_(T)modulated signals from transmitters 222 a through 222 t are thentransmitted from N_(T) antennas 224 a through 224 t, respectively.

At receiver system 250, the transmitted modulated signals are receivedby N_(R) antennas 252 a through 252 r and the received signal from eachantenna 252 is provided to a respective receiver (RCVR) 254 a through254 r. Each receiver 254 conditions (e.g., filters, amplifies, anddownconverts) a respective received signal, digitizes the conditionedsignal to provide samples, and further processes the samples to providea corresponding “received” symbol stream.

An RX data processor 260 then receives and processes the N_(R) receivedsymbol streams from N_(R) receivers 254 based on a particular receiverprocessing technique to provide N_(T) “detected” symbol streams. The RXdata processor 260 then demodulates, deinterleaves, and decodes eachdetected symbol stream to recover the traffic data for the data stream.The processing by RX data processor 260 is complementary to thatperformed by TX MIMO processor 220 and TX data processor 214 attransmitter system 210.

A processor 270 periodically determines which pre-coding matrix to use(discussed below). Processor 270 formulates a reverse link messagecomprising a matrix index portion and a rank value portion.

The reverse link message may comprise various types of informationregarding the communication link and/or the received data stream. Thereverse link message is then processed by a TX data processor 238, whichalso receives traffic data for a number of data streams from a datasource 236, modulated by a modulator 280, conditioned by transmitters254 a through 254 r, and transmitted back to transmitter system 210.

At transmitter system 210, the modulated signals from receiver system250 are received by antennas 224, conditioned by receivers 222,demodulated by a demodulator 240, and processed by a RX data processor242 to extract the reserve link message transmitted by the receiversystem 250. Processor 230 then determines which pre-coding matrix to usefor determining the beamforming weights then processes the extractedmessage.

Turning to FIG. 3, this figure shows an alternative simplifiedfunctional block diagram of a communication device according to oneembodiment of the invention. As shown in FIG. 3, the communicationdevice 300 in a wireless communication system can be utilized forrealizing the UEs (or ATs) 116 and 122 in FIG. 1 or the base station (orAN) 100 in FIG. 1, and the wireless communications system is preferablythe LTE or NR system. The communication device 300 may include an inputdevice 302, an output device 304, a control circuit 306, a centralprocessing unit (CPU) 308, a memory 310, a program code 312, and atransceiver 314. The control circuit 306 executes the program code 312in the memory 310 through the CPU 308, thereby controlling an operationof the communications device 300. The communications device 300 canreceive signals input by a user through the input device 302, such as akeyboard or keypad, and can output images and sounds through the outputdevice 304, such as a monitor or speakers. The transceiver 314 is usedto receive and transmit wireless signals, delivering received signals tothe control circuit 306, and outputting signals generated by the controlcircuit 306 wirelessly. The communication device 300 in a wirelesscommunication system can also be utilized for realizing the AN 100 inFIG. 1.

FIG. 4 is a simplified block diagram of the program code 312 shown inFIG. 3 in accordance with one embodiment of the invention. In thisembodiment, the program code 312 includes an application layer 400, aLayer 3 portion 402, and a Layer 2 portion 404, and is coupled to aLayer 1 portion 406. The Layer 3 portion 402 generally performs radioresource control. The Layer 2 portion 404 generally performs linkcontrol. The Layer 1 portion 406 generally performs physicalconnections.

As noted in the 3GPP RAN2 #104 Chairman's Note, 3GPP RAN2 #104 meetingmade the following agreements on NR (New RAT/Radio) eV2X (enhancedVehicle to Everything) sidelink communications:

Agreements 1: NR V2X sidelink communication is supported for allRRC_CONNECTED UEs, RRC_IDLE UEs and RRC_INACTIVE UEs (if supported). AUE in RRC_INACTIVE (if supported) performs V2X sidelink communicationfollowing the same way as RRC_IDLE UEs, i.e. using cell-specificconfigurations included in SIB. 2: As in LTE, V2X-specific SIB(s) isneeded for NR V2X. It is FFS by RAN2 whether V2X-specific SI should beon-demand SI or not for a cell supporting V2X sidelink communication inNR. 3: For RRC connection establishment for NR V2X sidelinkcommunication, the RRC connection establishment condition for LTE V2Xsidelink communication (i.e. concerned frequency included in SIB withoutTx pool) is taken as the baseline. It is FFS whether/what new RRCconnection establishment condition(s) for V2X sidelink communication areneeded in NR, on top of the LTE baseline. 4: RAN2 will support the casea UE can be configured to perform both mode-1 and mode-2 at the sametime assuming RAN1 does not have concern on it. FFS on the scenariowhich it is applicable. 5: For NR V2X sidelink communication duringhandover, the Tx and Rx operations and configurations during handover inLTE V2X sidelink communication (i.e. using Rx pool and exceptional Txpool of the target cell configured in HO command) are taken as thebaseline. Enhancements for the Tx/Rx operations and configurationsduring handover are needed for NR V2X sidelink communication, on top ofthe LTE baseline. Details are FFS. 6: For cell (re)selection in NR V2Xsidelink communication, the cell reselection criterion (i.e.prioritizing frequency giving inter-carrier V2X SL configuration) andconfiguration (i.e. SL-AnchorCarrierFreqList-V2X) in LTE V2X sidelinkcommunication are taken as the baseline. Regarding the cell(re)selection for V2X sidelink communication in NR, it is FFSwhether/what new criterion/configuration is needed on top of the LTEbaseline. It is up to UE implementation how to minimize thetransmission/reception interruption for NR V2X sidelink communicationduring cell (re)selection. 7: For NR V2X sidelink communication, thereporting of sidelink UE information is needed. The sidelink UEinformation reporting mechanism in LTE is taken as the baseline. Forsidelink UE information in NR, it is FFS what information needs to beincluded. 8: For sidelink related measurement and reporting in NR, CBRmeasurement and reporting as well as location reporting are needed. TheCBR measurement/reporting mechanism and location reporting mechanism(FFS whether NR signaling supports it) for LTE V2X sidleinkcommunication are taken as the baseline. RAN2 may decide whether anyenhancements are needed for sidelink related measurement and reportingmechanism in NR on top of the LTE baseline depending on RAN1 progress.9: To report the traffic pattern(s) for NR V2X sidelink communication,UE assistance information reporting is needed (at least for periodictraffic pattern). The UE assistance reporting mechanism for LTE V2Xsidelink communication is taken as the baseline. RAN2 to further discusswhether/what new information is needed in UE assistance information forNR V2X sidelink communication, on top of the LTE baseline, based on theconclusion of QoS discussion. 10:  RAN2 wait for RAN1 conclusions on SLsynchronization design before working on the MIB-SL-V2X design in NR PC5RRC. 11:  In NR, PC5-C protocol stack includes at least RRC, RLC, MACand PHY sub-layers. Whether to have PDCP sub-layer depends on whetherany new PCS RRC message other than MIB-SL is introduced (e.g. outcome of[103bis#38]). Agreements on MAC: 1: RAN2 will capture L2 packetfiltering function with the condition (i.e. if full L1 id is not used inL1 control information). It is FFS whether we need additional filteringfunction for unicast and groupcast. 2: Sidelink carrier/resource(re-)selection function is supported in NR MAC at least for NR Sidelinkbroadcast. RAN2 should further study whether LTE operation can be reusedfor Sidelink carrier/resource (re-)selection function in NR, consideringRAN1 progress. 3: Sidelink HARQ transmissions (w/o HARQfeedback) andSidelink process are supported at least for NR sidelink broadcast. RAN2should further discuss potential enhancements to sidelink HARQoperation, considering RAN1 progress. 4: Sidelink specific LCP issupported at least for NR sidelink broadcast in NR MAC. RAN2 shouldfurther study how Sidelink specific LCP will work. 5: Sidelink BufferStatus Reporting is supported for NR sidelink broadcast, groupcast andunicast in NR MAC. 6: UL/SL TX prioritization is supported for NRsidelink broadcast, groupcast and unicast in NR MAC. Study potentialimprovements to UL/SL TX prioritization, if necessary e.g. due topotential impact on QoS. 7: RAN2 should additionally study whether andhow to enhance SR procedure/configuration, MAC PDU format, HARQ/CSIfeedback/ procedure (for groupcast and unicast) (if there is any stage 2RAN2 issue), and configured SL grant transmission in NR MAC. Agreementson RLC: 8: Segmentation and reassembly of RLC SDUs are supported in NRRLC for NR sidelink broadcast, groupcast and unicast. 9: RLC SDU discardfunction is supported in NR RLC for NR sidelink broadcast, groupcast andunicast. 10:  If SBCCH is used for NR sidelink (dependent on RAN1decision on synchronization aspect), a NR TM RLC entity is configured tosubmit/receive RLC PDUs. 11:  A NR UM RLC entity is configured tosubmit/receive RLC PDUs, for user packets of SL broadcast, groupcast andunicast. RLC AM is not supported for broadcast. Agreements on PDCP: 12: Sidelink packet duplication is supported in NR PDCP for NR sidelinkbroadcast, groupcast. FFS on unicast. 13:  Timer based SDU/PDU discardfunction is supported in NR PDCP for NR sidelink broadcast, groupcastand unicast. Agreements on unicast 1: For AS-level information requiredto exchange among UEs via sidelink for SL unicast, RAN2 can consider thefollowings as a baseline and will check if the AS- level information canbe agreed and the details after some progress in RAN2, SA2 and RAN1: UEID, UE capability, Radio/Bearer configuration, PHYinformation/configuration (e.g. HARQ, CSI), Resourceinformation/configuration and QoS info 2: AS-level information for SLunicast can be exchanged between gNB and UE for RRC configuration. RAN2assumes that a UE can provide network with QoS related information andwill check if the AS-level information can be agreed and the detailsafter some progress in RAN2, SA2 and RAN1. 3: AS-level information isexchanged via RRC signalling (e.g. PC5-RRC) among UEs via sidelink forSL unicast. New logical channel (SCCH: SL Control Channel) in additionto STCH (SL Traffic Channel) will be also introduced. SCCH carriersPC5-RRC messages. 4: RAN2 will consider both options during SI phase.Further discussion on the definition, procedure and information for eachoption is needed. Option 1: AS layer connection establishment procedureby PC5-RRC is also needed. Option 2: Upper layer connectionestablishment procedure is enough. 5: RAN2 will study a kind of RRM orRLM based AS level link management. RAN2 will not consider a kind ofPC5-RRC level keep alive message based management. Further discussion onpossible detailed options is needed. Agreements on groupcast 6: Furtherdiscussion is needed on whether groupcast follows same mechanism forunicast, which are agreed in the above. 7: No AS-level mechanism todetermine a group manager (i.e. head UE) is stuided. FFS for platooning,on the visibility of a group manager (head UE) to AS and AS- levelfunctionalities. Agreements 1: RAN2 assumes that the candidate RAT(s)with SL should be associated with service type by upper layer. 2: RAN2assumes for a given V2X service type, it may be associated with: 1) LTERAT only, 2) NR RAT only, FFS on 3) LTE or NR RAT and 4) LTE and NR RAT.We can ask SA2 suggestion/guideline on 3) and 4). 3: RAN2 assumes Txprofile based approach is considered as baseline for RAT selection ofSL. RAN2 is suggested to further discuss the RAN2 impacts of V2X servicetype and RAT mapping approach. 4: RAN2 assumes RAT selection is onlyapplied to V2X broadcast and for any V2X unicast and groupcast service,it is communicated over NR only. We will ask if SA2 has anyconcern/feedback on it. 5: The availability of Uu/PC5 will be informedto upper layer and the upper layer performs the Uu/PC5 interfaceselection. FFS on what availability implies, how AS to decideavailability of Uu/PC5 and whether we need to specify it.

3GPP TR 23.786 V1.0.0 introduced the following solutions for eV2Xcommunications:

6.11 Solution #11: Solution for Unicast or Multicast for eV2XCommunication Over PC5 Reference Point

6.11.1 Functional Description

This solution addresses Key Issue #1 on the support of eV2X GroupCommunication, Key Issue #9 on the support of the unicast/multicastcommunication over PC5 and Key Issue #4 on the support of PC5 QoSframework enhancement for eV2X, focusing on the following aspects:

-   -   Identifiers for the unicast communication, e.g. L2 ID;    -   Signaling protocol to support unicast/multicast communication;    -   QoS support and AS layer configurations;    -   Security associations;    -   Procedures for the link establishment and maintenance.

6.11.2 Solution Description 6.11.2.1 Identifiers for the UnicastCommunication

6.11.2.1.1 Separate L2 ID Address Space for Unicast and Multicast fromThose for Broadcast

One of the essential identifiers for the unicast/multicast communicationis the L2 ID. As of the ProSe design in TS 23.303 [8], the destinationL2 ID address space for one-to-one communication and one-to-manycommunications are separate with AS layer mechanism, i.e. MAC layerversion number. This is done to avoid conflicts of the address used thatmay cause harm to one-to-one communications. In a similar manner, V2Xunicast should also use the separate L2 IDs than that for the broadcastand multicast.

This separation applies to both destination L2 ID and source L2 ID. Fora UE that has both broadcast and unicast/multicast traffic, different L2IDs should be used with corresponding formats. The source L2 ID will beused by peer UE as the destination L2 ID in unicast communication.Details of the related L2 ID management for unicast/multicast isdescribed in following clauses.

The UE may use distinct source L2 ID for different unicast one to onecommunication link e.g. when different unicast links are associated withdifferent upper layer identifiers.

6.11.2.1.2 Deciding the Destination L2 ID to Use for Unicast/MulticastCommunication 6.11.2.1.2.1 Option A

In TS 23.285 [5], the Destination L2 ID is decided by the UE based on aconfigured mapping between PSID/ITS-AID to the L2 ID. This suites forbroadcast traffic, but does not work for unicast or multicast traffic.In unicast or multicast, destination L2 ID would not be decided based onPSID/ITS-AID. A V2X UE should be allowed to have multiple unicastconnections or multicast groups supported simultaneously for aparticular service (PSID/ITS-AID). Therefore, the destination L2 IDinformation in this case should come from the upper layer. This meansthat the interface between the V2X layer and upper layer needs to beenhanced to allow such information to be passed down together with thedata packet.

It is expected that the actual V2X applications do not understand thenotion of L2 ID, as the applications can be built for cross technologyor platforms. Therefore, some mid-ware layer within the UE has totranslate the identifier used by the application layer, e.g. Station ID,to the V2X L2 ID. It means such mid-ware layer needs to maintain themapping of application layer destination identifiers and L2 IDs. Sincethis mid-ware layer is out of scope of SA2, in the specification it canbe noted as “upper layer” in general, and the assumption that this“upper layer” maintains the mapping and provides the L2 ID for unicastor multicast communication should be documented.

6.111.1.2.2 Option B

An alternative to the above solution is for the V2X layer to manage suchunicast link/multicast group to L2 ID mapping. In that case, the unicastlink/multicast group can be allocated with a flow identifier at the timeof establishment. Corresponding connection profile information, e.g. L2IDs, transmission settings, QoS parameters, etc., could be associatedwith it. In such a case, the upper layer only needs to use the flowidentifier to indicate the destination and pass it down with the datapacket. V2X layer will apply the associated profile information,including the L2 IDs, for the transmission. This would allow the reusethe Uu link handling mechanisms, e.g. similar to that of the QoS Flows,and be more extensible. Again, the translation of the application layeridentifiers, e.g. Station ID, to this flow identifier has to be done bythis mid-ware layer, i.e. the “upper layer”.

6.111.2 Signaling Protocol to Support Unicast/Multicast Communication

For unicast or multicast communication, there is a need for some controlmessage exchanged between the UEs involved in order to establish thelink or group. Therefore, some signaling protocol is required.

In ProSe one-to-one communication defined in TS 23.303 [8], a PC5Signaling Protocol (clause 5.1.1.5.2) was introduced, which runs overPDCP layer. Although it is defined for ProSe use, the messages could beextended in order to be used for V2X communication. The detailedprotocol design needs to be reviewed based on the actual unicastoperation procedures. Another alternative approach is to run RRC overPC5. As PC5 Signaling Protocol is used over PDCP anyway, RRC protocolcan be used to replace it. Although not all RRC features are requiredfor PC5 operation, those selected V2X relevant RRC messages can beextended and used, e.g. SidelinkUEInformation, etc. The advantage ofthat is the potential unification of control signaling protocols for Uuand PC5.

Therefore, in this solution a signaling protocol over PC5 for theunicast/multicast communication management is introduced.

6.11.2.3 QoS Support and AS Layer Configurations

It is desirable that QoS can be support over the unicast and multicastcommunication as well. In TS 23.285 [5], the QoS model for V2Xcommunication is based on the per packet model, e.g. PPPP and PPPR. Withunicast or multicast communication, it should be discussed whether aconnection-oriented QoS model similar to that of Uu connection should besupported as well. As also discussed in Key Issue #4 “Support of PC5 QoSframework enhancement for eV2X”, something more than existing PPPP andPPPR is expected be required.

Specifically for unicast or multicast, due to the link or groupinvolved, most packets sent over the same unicast link between a pair ofpeers should have the same QoS characteristics. This is closer to the Uuconnection model, rather than the normal broadcast based traffic.Therefore, Uu type of QoS management concept can be reused here. Thisallow a unified model for Uu and PC5.

In addition, there could be different AS layer features that may beoptional or not backward compatible. Therefore, when setting up theunicast link, such configuration could be also negotiated and configuredtogether with/or as part of the QoS profile.

-   -   NOTE: The QoS Model for unicast described in Solution #19        (clause 6.19) is used.

6.11.2.4 Security Associations

The unicast or multicast communication may need protection at link layeras well. The ProSe one-to-one communication supports secure L2 linkestablishment, as defined in TS 33.303 [11]. However, within V2Xcommunication context, each UE has the corresponding certificates forthe security protection. Therefore, there may be a need to enhancementor adjust the existing L2 secure link establishment protocol in order tosupport the use of such security associations. The exact securityhandling should be analysed and decided by SA3. SA2 design needs to bealigned with those decisions when available.

6.11.2.5 Procedures for the Link Establishment and Maintenance

TS 23.303 [8] has defined the procedures for the establishment andmaintenance of secure L2 link over PC5, as in clause 5.4.5. Theseprocedures can be enhanced and adapted for the V2X use, subject to thedecisions above regarding signaling protocol choice, security handling,etc. Some addition considerations for the V2X for the link/grouphandling is required though. For V2X communication, not all UEs will besupporting or use unicast communication. In addition, not all servicesmay be run over the same channel or RAT (e.g. LTE V2X vs. NR V2X). WithV2X, there is no discovery channel like that of ProSe (i.e. PC5-D), andthere is no assumption on the configuration from network as that ofPublic Safety use. Therefore, in order to support the linkestablishment, there is a need for service announcement in order toinform the peer of the existence of the UE and the capability of the UEfor the unicast communication, e.g. channel to operate, or the servicessupported, etc.

Such a service announcement should be made accessible to all the UEsthat are interested in using the service. For example, such announcementcould be either configured to send over a dedicate channel, similar tohow WAVE Service Advertisement (WSA) is handled, or to be piggybacked onthe periodical messages from the supporting UEs.

-   -   NOTE 1: Service announcement is handled by upper layer and out        of scope of SA2.

For layer 2 link maintenance, keep-alive functionality is needed todetect that when the UEs are not in direct communication range, so thatthey can proceed with implicit layer 2 link release.

-   -   NOTE 2: It is left to Stage 3 to determine how keep-alive        functionality is supported.

6.11.3 Procedures 6.11.3.1 Establishment of Layer 2 Link Over PC5

Layer-2 link establishment procedure as defined in TS 23.303 [8] clause5.4.5.2 can be reused for the eV2X unicast link establishment, with thefollowing adaptations:

-   -   The messages may be converted to RRC signaling message instead        of PC5 signaling message, depends on RAN WG's decision.    -   “UE oriented layer 2 link establishment” operates as below and        Figure 6.11.3.1-1 shows the procedure:    -   The Direct Communication Request message can be sent by UE-1        with broadcast mechanism, i.e. to a broadcast address associated        with the application instead of the L2 ID of UE-2. The upper        identifier of UE-2 is included in the Direct Communication        Request message to allow UE-2 to decide on if to respond to the        request. The Source L2 ID of this message should be the unicast        L2 ID of the UE-1.    -   The Direct Communication Request message should be transmitted        using default AS layer setting e.g. broadcast setting, that can        be understood by UE-2.    -   UE-2 uses the source L2 ID of the received Direct Communication        Request message as destination L2 ID in the subsequent signaling        to UE-1, and uses its own unicast L2 ID as the source L2 ID.        UE-1 obtains UE-2's L2 ID for future communication, for        signaling and data traffic.

Figure 6.11.3.1-1 of 3GPP TR 23.786 V1.0.0, Entitled “UE Oriented Layer2 Link Establishment Procedure”, is Reproduced as FIG. 5

-   -   “V2X Service oriented layer 2 link establishment” operates same        to the “UE oriented layer 2 link establishment” with the        following differences and Figure 6.11.3.1-2 shows the procedure:        -   The information about V2X Service requesting L2 link            establishment, i.e. information about the announced V2X            Service is included in the Direct Communication Request            message to allow other UEs to decide on if to respond to the            request.        -   The UEs that are interested in using the V2X Service            announced by the Direct Communication Request message can            respond to the request (UE-2 and UE-4 in Figure 6.11.3.1-2).        -   After establishing layer 2 link with other UE(s) as            described above, new UE(s) can enter proximity with UE-1,            i.e. UE-1's direct communication range. In this case, UE-1            may initiate V2X Service oriented layer 2 link establishment            procedure as it is aware of new UE(s) from Application Layer            messages sent by the UE(s). Or the new UE may initiate V2X            Service oriented layer 2 link establishment procedure.            Therefore, UE-1 does not have to keep sending a Direct            Communication Request message periodically to announce the            V2X Service it wants to establish L2 link with other UE for            unicast.

Figure 6.11.3.1-2 of 3GPP TR 23.786 V1.0.0, Entitled “V2X ServiceOriented Layer 2 Link Establishment Procedure”, is Reproduced as FIG. 6

The layer 2 link supports the non-IP traffic. No IP address negotiationand allocation procedure would be carried out.

6.11.3.2 Contents of the Signaling Message for Link Establishment

The information carried in Direct Communication Request message definedin TS 24.334 [13] requires at least the following updates:

-   -   For “UE oriented layer 2 link establishment”,        -   The User Info needs to include the target UE's ID (UE-2's            upper layer ID), besides the initiating UE's ID (UE-1's            upper layer ID).    -   NOTE: Stage 3 can decide if these IDs can be carried in the same        IE or separate IEs, for example, the Station ID/Vehicle Temp ID        only needs to be 4 octets.    -   For “V2X Service oriented layer 2 link establishment”,        -   The Announced V2X Service Info needs to include the            information about V2X Service requesting L2 link            establishment, e.g. PSID or ITS-AIDs of the V2X application.            Sensor Sharing, and etc can be the case for the V2X Service.    -   The IP Address Config, which is specified as mandatory for        ProSe, should allow an indication that no IP is to be used, such        that the receiving UE (e.g. UE-2) would not start any IP        configuration procedure for this particular link.    -   The IEs dedicated for security need to be reviewed by SA3, as        the security mechanism for eV2X may be different and requires        different IEs.    -   Additional configuration information regarding the link, e.g.        when RRC message is used there may be AS layer configurations.

6.11.3.3 Link Identifier Update Procedure for Privacy Protection ofUnicast Communication Figure 6.11.3.3-1 of 3GPP TR 23.786 V1.0.0,Entitled “Layer-2 Link Identifier Update Procedure”, is Reproduced asFIG. 7

This procedure is used to update the peer in the unicast communicationof the impending change of the identifiers used for this link. Due tothe privacy requirements, in eV2X use, UE should frequently change itsidentifiers in order to avoiding being trackable by 3rd party. When theidentifier change happens, all identifiers across all the layers, i.e.from application layer ID to L2 ID, need to be changed. This signalingis required before the identifier changes happen, to prevent serviceinterruptions.

-   -   1. UE-1 decides the change of identifiers, e.g. due to the upper        layer identifier change or a timer, and includes the new        identifiers to use (including the new upper layer identifiers,        new IP address/prefix if application, new L2 IDs) in the Link        Identifier Update Request message, and send to UE-2 before it        changes the identifiers. The new identifiers to use should be        cyphered to protect privacy.    -   NOTE 1: The timer is running on a per Source L2 ID.    -   2. UE-2 respond with a Link Identifier Update Response message.        Upon reception of the message, UE-1 and UE-2 can start to use        the new identifiers for the data traffic. UE-1 shall receive        traffic on its old L2 ID until it receives the Link Id Update        Response from UE-2.    -   NOTE 2: If there are multiple links from UE-1 using the same        upper layer identifiers or L2 IDs,        -   UE-1 needs to perform the update procedure over each of the            link and for each link needs to keep receiving traffic on            its old L2 ID for that specific link until it receives the            Link Id Update Response.

6.11.3.4 Security Aspects for Layer 2 Link

As the eV2X applications have associated security certificates, theunicast link can reuse those to derive the security association forprotecting the signaling or data of the unicast link.

6.11.4 Impact on Existing Entities and Interfaces

-   -   Editor's note: Impacts on existing nodes or functionality will        be added.

6.11.5 Topics for Further Study

None.

6.11.6 Conclusions

Solution documented in clauses 6.11.1 to 6.11.4 addressed all theaspects of Key Issue #9 Support of unicast/multicast for sensor sharingover PC5, and should move to normative phase. Following aspects will befurther updated based on feedbacks from other Working Groups:

-   -   the signaling message definition for unicast link establishment        and management, e.g. if and how RRC signaling is used for        unicast link;    -   the choice of per packet QoS model or bearer based QoS model for        broadcast, groupcast, and unicast based on RAN decisions;    -   signal to the base station regarding the service used when        network scheduled mode is used;    -   the potential security related procedure updates for unicast        communication over PC5.    -   NOTE: The application layer may use unicast or groupcast        communication mechanism for different applications, e.g.        platooning applications.

[ . . . ]

6.19 Solution #19: QoS Support for eV2X Communication Over PC5 Interface

6.19.1 Functional Description 6.19.1.1 General Description

This solution addresses Key Issue#4 (clause 5.4) Support of PC5 QoSframework enhancement for eV2X. The QoS requirements for eV2X aredifferent from that of the EPS V2X, and the previous defined PPPP/PPPRin TS 23.285 [5] are considered not to satisfy the needs. Specifically,there are much more QoS parameters to consider for the eV2X services.This solution proposes to use 5QI for eV2X communication over PC5interface. This allows a unified QoS model for eV2X services overdifferent links.

6.19.1.2 Solution Description

The new service requirements were captured in TS 22.186 [4]. The newperformances KPIs were specified with the following parameters:

-   -   Payload (Bytes);    -   Transmission rate (Message/Sec);    -   Maximum end-to-end latency (ms);    -   Reliability (%);    -   Data rate (Mbps);    -   Minimum required communication range (meters).

Note that the same set of service requirements apply to both PC5 basedV2X communication and Uu based V2X communication. As analysed inSolution #2 (clause 6.2), these QoS characteristics could be wellrepresented with 5QI defined in TS 23.501 [7].

It is therefore possible to have a unified QoS model for PC5 and Uu,i.e. also use 5QIs for V2X communication over PC5, such that theapplication layer can have a consistent way of indicating QoSrequirements regardless of the link used. This does not prevent the ASlayer from implementing different mechanisms over PC5 and Uu to achievethe QoS requirements. Considering the 5GS V2X capable UEs, there arethree different types of traffic: broadcast, multicast, and unicast.

The UE-PC5-AMBR is applied to all types of traffic and is used for theRAN for capping the UE PC5 transmission in the resources management.

For unicast type of traffic, it is clear that the same QoS Model as thatof Uu can be utilized, i.e. each of the unicast link could be treated asa bearer, and QoS flows could be associated with it. All the QoScharacteristics defined in 5QI and the additional parameter of data ratecould apply. In addition, the Minimum required communication range couldbe treated as an additional parameter specifically for PC5 use.

For broadcast traffic, there is no bearer concept. Therefore, each ofthe message may have different characteristics according to theapplication requirements. The 5QI should then be used in the similarmanner as that of the PPPP/PPPR, i.e. to be tagged with each of thepacket.

5QI is able to represent all the characteristics needed for the PC5broadcast operation, e.g. latency, priority, reliability, etc. A groupof V2X broadcast specific 5QIs (i.e. VQIs) could be defined for PC5 use.

-   -   NOTE 1: The 5QI used for PC5 may be different from that used for        Uu even for the same V2X service, e.g. the PDB for the PC5 can        be longer than that for the Uu as it is a direct link. The 5QIs        used for PC5 is named VQI for differentiation.    -   NOTE 2: A mapping between the EPS V2X QoS parameters, e.g. PPPP        and PPPR, with the new VQIs, e.g. similar to the non-GBR 5QIs        defined in TS 23.501 [7], will be defined in normative phase for        broadcast operation.    -   NOTE 3: The working assumption is that NR PC5 design support the        use of V2X 5QIs.    -   NOTE 4: AS layer may handle unicast, groupcast and broadcast        traffic by taking all their priorities, e.g. indicated by VQI,        into account.

6.19.1.3 V2X 5QI (VQI) Values for PC5 Broadcast Use

A set of new VQIs for V2X use will be defined in normative phasereflecting the service requirements documented in TS 22.186 [4].

-   -   NOTE 1: The working assumption is that non-standardized VQI is        not supported in this release.    -   NOTE 2: Whether per packet or per QoS flow QoS Model is used        depends on RAN decision.

6.19.2 Procedures

-   -   Editor's note: This clause describes procedures to use the new        QoS model for PC5 communication. It depends on RAN development        as well.

6.19.2.1 QoS Support for Unicast Communication Over PC5 Interface6.19.2.1.0 General

To enable Q05 support for eV2X one-to-one communication over PC5interface, the followings procedures need to be supported.

-   -   Editor's note: The following procedures may be further updated        depending on the progress on PC5 QoS Model.

6.19.2.1.1 QoS Parameters Provision to UE and NG-RAN

The PC5 QoS parameters and PC5 QoS rule are provisioned to the UE aspart of service authorization parameters using the solution defined forKey Issue #5. The PC5 QoS rule is used to map the V2X services (e.g.PSID or ITS-AIDs of the V2X application) to the PC5 QoS flow. The PC5QoS parameters retrieved by the PCF from the UDR are provided to theNG-RAN via AMF. The AMF stores such information as part of the UEcontext. For subsequent procedures (e.g., Service request, Handover),the provision of the PC5 QoS parameters via N2 will follow thedescription as per clause 6.6.2.

-   -   NOTE 1: The UE-PC5-AMBR is provided by the UDM and the details        will follow the description as per Solution #6.

The PC5 QoS parameters provisioning to the UE and NG-RAN could betriggered by the UE Policy container included in the NAS messageprovided by the UE. The PCF sends to the AMF the updated PC5 QoSparameters for NG-RAN when needed.

-   -   NOTE 2: The detailed PC5 QoS parameters used by NG-RAN will be        identified during the normative work phase.    -   NOTE 3: NG-RAN is configured with static parameters for network        scheduled resources allocation mode to support PC5 QoS.

6.19.2.1.2 QoS Parameters Negotiation Between UEs

The PC5 QoS parameters are negotiated at the establishment of one-to-onecommunication procedure, so the one-to-one communication establishmentprocedure defined in TS 23.303 [8] is enhanced to support PC5 QoSparameters negotiation between two UEs. After the PC5 QoS parametersnegotiation procedure, the same QoS is used in both directions.

Figure 6.19.2.1.2-1 of 3GPP TR 23.786 V1.0.0, Entitled “Establishment ofSecure Layer-2 Link Over PC5”, is Reproduced as FIG. 8

UEs engaged in one to one communication negotiate PC5 QoS parametersduring the link establishment procedure.

-   -   1. UE-1 sends a Direct Communication Request message to UE-2 in        order to trigger mutual authentication. This message includes        the requested PC5 QoS parameters.    -   2. UE-2 initiates the procedure for mutual authentication. The        UE-2 includes the accepted PC5 QoS parameters in the Response        message.    -   NOTE: This procedure is aligned with Solution #11 (clause 6.11).        6.19.2.1.3 QoS Handling for eV2X Communication

When PC5 unicast is used for the transmission of eV2X messages, thefollowing principles are applied for both network scheduled operationmode and UE autonomous resources selection mode:

-   -   PC5 QoS parameters defined in clause 6.19.1.2 applies to the        eV2X communication over PC5.    -   The eV2X message is sent on the PC5 QoS flow established using        the procedure described in clause 6.19.2.1.2.    -   The mapping of application layer eV2X message to PC5 QoS        parameters is based on the PC5 QoS rule.

When the network scheduled operation mode is used, following additionalprinciples apply:

-   -   UE provides PC5 QoS parameter information to the gNB for        resources request.    -   When the gNB receives a request for PC5 resource from a UE, the        gNB can authorize the requested PC5 QoS parameter based on the        PC5 QoS parameters received from AMF.    -   gNB can use the PC5 QoS parameter information for PC5 QoS        handling.

When the autonomous resources selection mode is used, followingadditional principle applies:

-   -   The UE can use the PC5 QoS parameter for PC5 QoS handling based        on the provisioned information described in clause 6.19.2.1.1.

6.19.2.2 QoS Support for Broadcast Communication Over PC5 Interface

When PC5 broadcast is used for the transmission of eV2X messages, thefollowing principles are followed for both network scheduled operationmode and UE autonomous resources selection mode:

-   -   PC5 QoS parameters (e.g. VQI) defined in clause 6.19.1.2 applies        to the eV2X communication over PC5.    -   The application layer sets the PC5 QoS parameters for each eV2X        message when passing it to V2X layer for transmission.

When the network scheduled operation mode is used, following additionalprinciples apply:

-   -   UE provides PC5 QoS information reflecting PC5 QoS parameters to        the gNB for resources request.    -   gNB can use the PC5 QoS information reflecting PC5 QoS        parameters for QoS handling.

When the autonomous resources selection mode is used, followingadditional principle applies:

-   -   The UE can use the PC5 QoS parameters for PC5 QoS handling.    -   NOTE: The choice of per packet QoS model or bearer based QoS        model for broadcast is based on RAN decisions.

6.19.2.3 QoS Support for Group Communication Over PC5 Interface

The procedure on QoS support for group communication over PC5 interfaceis described in clause 6.21.2 (Solution #21).

6.193 Impact on Existing Entities and Interfaces

Following are the impacts to the UE and other NFs:

-   -   UE needs to support new QoS model for PC5 communication.    -   AMF provides NG-RAN with the QoS parameters for PC5        communication fetched from PCF in associating N2 messages for        different procedures.    -   NG-RAN receives QoS parameters for PC5 communication from AMF        and enforces QoS parameter for the network schedule mode.    -   UDR stores QoS parameters for PC5 communication.    -   Editor's note: It is FFS if mapping of PPPP, PPPR to the new VQI        would be necessary for broadcast traffic.

6.19.4 Topics for Further Study

-   -   Editor's note: This clause describes topics for further study.

6.19.5 Conclusions

The solution captured in clauses 6.19.1 to 6.19.3 should move tonormative phase.

3GPP TS 36.321 V15.3.0 States:

6.1.3.1a Sidelink BSR MAC Control Elements

Sidelink BSR and Truncated Sidelink BSR MAC control elements consist ofone Destination Index field, one LCG ID field and one correspondingBuffer Size field per reported target group.

The Sidelink BSR MAC control elements are identified by MAC PDUsubheaders with LCIDs as specified in table 6.2.1-2. They have variablesizes.

For each included group, the fields are defined as follows (figures6.1.3.1a-1 and 6.1.3.1a-2):

-   -   Destination Index: The Destination Index field identifies the        ProSe Destination or the destination for V2X sidelink        communication. The length of this field is 4 bits. The value is        set to the index of the destination reported in        destinationInfoList for sidelink communication or is set to one        index among index(es) associated to same destination reported in        V2X-DestinationInfoList for V2X sidelink communication. If        multiple such lists are reported, the value is indexed        sequentially across all the lists in the same order as specified        in [8];    -   LCG ID: The Logical Channel Group ID field identifies the group        of logical channel(s) which buffer status is being reported. The        length of the field is 2 bits;    -   Buffer Size: The Buffer Size field identifies the total amount        of data available across all logical channels of a LCG of a        ProSe Destination after all MAC PDUs for the TTI have been        built. The amount of data is indicated in number of bytes. It        shall include all data that is available for transmission in the        RLC layer and in the PDCP layer; the definition of what data        shall be considered as available for transmission is specified        in [3] and [4] respectively. The size of the RLC and MAC headers        are not considered in the buffer size computation. The length of        this field is 6 bits. The values taken by the Buffer Size field        are shown in Table 6.1.3.1-1;    -   R: Reserved bit, set to “0”.

Buffer Sizes of LCGs are included in decreasing order of the highestpriority of the sidelink logical channel belonging to the LCGirrespective of the value of the Destination Index field.

Figure 6.1.3.1a-1 of 3GPP TS 36.321 V15.3.0, Entitled “Sidelink BSR andTruncated Sidelink BSR MAC Control Element for Even N”, is Reproduced asFIG. 9 Figure 6.1.3.1a-2 of 3GPP TS 36.321 V15.3.0, Entitled “SidelinkBSR and Truncated Sidelink BSR MAC Control Element for Odd N”, isReproduced as FIG. 10

In the 3GPP RAN2 #104 Chairman's note, a solution for unicast (i.e.one-to-one) or multicast (i.e. one-to-many) for V2X communication overPC5 reference point was introduced. Based on this solution, a UE-1 (i.e.the initiating UE) transmits a Direct Communication Request message to aUE-2 (i.e. the target UE) during a layer-2 link establishment used forunicast link establishment. In response to reception of the DirectCommunication Request message, UE-2 responses a Direct CommunicationAccept to the UE-1. As illustrated in FIG. 11 and discussed below,phases of one-to-one sidelink communication for V2X service on top ofthe solution in the 3GPP RAN2 #104 Chairman's note are introduced:

I. Preamble (Illustrated in FIG. 12)

In this phase, UE-1 may be in RRC_CONNECTED state (or mode). In caseUE-1 is interested in V2X service(s), the UE-1 could request corenetwork (e.g. V2X Control Function) for service authorization. Possibly,UE-1 could be provided or configured with PC5 QoS (Quality of Service)information (e.g. PC5 5QI/QoS parameters, PC5 QoS rule, etc.) for theV2X service(s) during the service authorization. After complete of theservice authorization, UE-1 could be aware of the presence of UE-2 via,such as a discovery procedure or a one-to-many sidelink communication(i.e. reception of a V2X message transmitted by the UE-2 in proximity ofUE-1). It is noted that 5QI (5G QoS identifier) may also be called VQI(V2X QoS identifier).

II. SL LCH Configuration for PC5 Signaling (Illustrated in FIG. 13)

In one embodiment, a V2X application in the UE-1 may trigger aone-to-one sidelink communication to the UE-2. In this situation, itcould transmit a first RRC (Radio Resource Control) message (i.e.SidelinkUEInformation) to a base station (or gNB) to request assignmentof transmission resources for PC5 control signaling.

In the first RRC message, the content could include at least one of thefollowing:

-   A destination identity of the UE-2, which may be included in a    destination list;-   An identity of the V2X application (e.g. ITS-AID); and/or-   An identity of the service provided by the V2X application (e.g.    PSID).

In response to reception of the first RRC message, base station couldtransmit a second RRC message (e.g. RRCConnectionReconfiguration) to theUE-1 to assign RRC configuration.

In the second RRC message, the content could include at least one of thefollowing:

-   Identity of a sidelink logical channel used for PC5 control    signaling, e.g. SCCH (Sidelink Control Channel);-   Priority of the sidelink logical channel; and/or-   Identity of a logical channel group (LCG) for the sidelink logical    channel.

With the second RRC message, UE-1 could create a sidelink logicalchannel used for PC5 control signaling. The sidelink logical channelcould be used for transmission of a Direct Communication Request messageto the UE-2. The Direct Communication Request message could be a RRCmessage or a NAS (Non-Access Stratum) message.

III. One-to-One Sidelink Communication Link Establishment (Illustratedin FIG. 14)

When the Direct Communication Request message is available for sidelinktransmission, UE-1 could transmit a sidelink buffer status report to thebase station for allocating sidelink resource for the sidelinktransmission of the Direct Communication Request message. After thesidelink resource for the sidelink transmission of the DirectCommunication Request message is received, UE-1 could perform thesidelink transmission based on the sidelink resource.

In one embodiment, the Direct Communication Request message couldinclude at least one of the following:

-   An identity of the V2X application used to indicate the UE-2 which    application to activate;-   An identity of the service provided by the V2X application used to    indicate the UE-2 which service to activate;-   (Requested) PC5 5QI of a QoS flow for the V2X application or V2X    service; and/or-   (Requested) PC5 QoS parameters/levels/profiles of a QoS flow for the    V2X application or V2X service.

UE-1 could receive a Direct Communication Accept message from the UE-2.Possibly, the Direct Communication Accept message could include at leastone of the following:

-   (Accepted) PC5 5QI of a QoS flow for the V2X application or V2X    service;-   (Accepted) PC5 QoS parameters/levels/profiles of a QoS flow for the    V2X application or V2X service.

After exchanging the Direct Communication Request message and the DirectCommunication Accept message, UE-1 and the UE-2 could perform an IPaddress configuration procedure for determining 5-tuple (e.g. source IPaddresses, destination IP addresses, source port number, destinationport number and protocol ID) for the one-to-one sidelink communication.It may also be possible that IP address configuration procedure is donewith the Direct Communication Request message and the DirectCommunication Accept message (i.e. both procedures are combined intoone).

IV. STCH Configuration (Illustrated in FIGS. 15A-15D)

As illustrated in FIG. 15A, after finishing the one-to-one sidelinkcommunication link establishment, UE-1 could transmit a RRC message(e.g. UEAssistanceInformation) to the base station to request assignmentof transmission resources for the one-to-one sidelink communication.

In the RRC message, the content could include at least one of thefollowing:

-   An identity of the UE-2;-   An identity of the V2X application;-   An identity of the service provided by the V2X application;-   PC5 5QI of a QoS flow for the V2X application or V2X service; and/or-   PC5 QoS parameters, levels, or profiles of a QoS flow for the V2X    application or V2X service.

With the RRC message, the base station could verify the PC5 5QI of theQos flow and/or the PC5 QoS parameters, levels, or profiles of the QoSflow with a core network (e.g. V2X Control Function). The base stationcould then transmit a reconfiguration message (e.g.RRCConnectionReconfiguration, a RRC message) to UE-1 in response toreception of the RRC message.

A list of sidelink logical channel (e.g. STCH (Sidelink TrafficChannel)) could be included in the reconfiguration message, and for eachsidelink logical channel the reconfiguration message could include atleast one of the following:

-   An identity of a sidelink logical channel used for sidelink traffic;-   A priority of the sidelink logical channel;-   An identity of a sidelink logical channel group (LCG) associated    with the sidelink logical channel; and/or-   An identity of a QoS flow mapped to the sidelink logical channel.

Based on the above reconfiguration message, UE-1 could create at least asidelink logical channel (e.g. STCH) for the one-to-one sidelinkcommunication. Furthermore, UE-1 could associate the sidelink logicalchannel with a corresponding sidelink LCG. Furthermore, UE-1 could storea mapping of a QoS flow to the corresponding sidelink logical channel.

As illustrated in FIG. 15B, if UE-1 and UE-2 are served by a same basestation, UE-1 and UE-2 could share the content of the reconfigurationmessage used by UE-1 (since QoS requirement should be the same for UE-1and UE-2 on the V2X application). UE-1 could transmit a PC5-RRC messageon a sidelink logical channel used for control signaling (e.g. SCCH) toUE-2. The content of the PC5-RRC message could be created based on thecontent of the reconfiguration message. The content of the PC5-RRCmessage could be applied by UE-2 for transmitting user traffic of theV2X application over the one-to-one sidelink communication between UE-1and UE-2.

A list of sidelink logical channel could be included in the PC5-RRCmessage, and for each sidelink logical channel, the PC5-RRC messagecould include at least one of the following:

-   An identity of a sidelink logical channel used for user traffic;-   A priority of the sidelink logical channel;-   An identity of a sidelink logical channel group (LCG) associated    with the sidelink logical channel; and/or-   An identity of a QoS flow mapped to the sidelink logical channel.

Based on the PC5-RRC message, UE-2 could create at least a sidelinklogical channel for the V2X application. Furthermore, UE-2 couldassociate the sidelink logical channel with a corresponding sidelinkLCG. In addition, UE-2 could store a mapping of a QoS flow to thecorresponding sidelink logical channel.

FIG. 16 is a flow chart 1600 according to one exemplary embodiment fromthe perspective of a first UE performing a one-to-one sidelinkcommunication with a second UE. In step 1605, the first UE receives adedicated signaling from a first network node, wherein the dedicatedsignaling includes a first sidelink configuration for the one-to-onesidelink communication. In step 1610, the first UE transmits a secondsidelink configuration to the second UE, wherein the second sidelinkconfiguration is generated based on the first sidelink configuration andused for the second UE to configure the one-to-one sidelinkcommunication.

Referring back to FIGS. 3 and 4, in one exemplary embodiment of a firstUE performing a one-to-one sidelink communication with a second UE, thedevice 300 includes a program code 312 stored in the memory 310. The CPU308 could execute program code 312 to enable the UE (i) to receive adedicated signaling from a first network node, wherein the dedicatedsignaling includes a first sidelink configuration for the one-to-onesidelink communication, and (ii) to transmit a second sidelinkconfiguration to the second UE, wherein the second sidelinkconfiguration is generated based on the first sidelink configuration andused for the second UE to configure the one-to-one sidelinkcommunication. Furthermore, the CPU 308 can execute the program code 312to perform all of the above-described actions and steps or othersdescribed herein.

FIG. 17 is a flow chart 1700 according to one embodiment from theperspective of a second UE performing a one-to-one sidelinkcommunication with a first UE, wherein the first UE is served by a firstnetwork node. In step 1705, the second UE receives a second sidelinkconfiguration from the first UE, wherein the second sidelinkconfiguration is used to configure the one-to-one sidelinkcommunication. In step 1710, the second UE performs a sidelinktransmission and/or a sidelink reception on the one-to-one sidelinkcommunication based on the second sidelink configuration.

Referring back to FIGS. 3 and 4, in one exemplary embodiment of a secondUE performing a one-to-one sidelink communication with a first UE,wherein the first UE is served by a first network node, the device 300includes a program code 312 stored in the memory 310. The CPU 308 couldexecute program code 312 to enable the UE (i) to receive a secondsidelink configuration from the first UE, wherein the second sidelinkconfiguration is used to configure the one-to-one sidelinkcommunication, and (ii) to perform a sidelink transmission and/or asidelink reception on the one-to-one sidelink communication based on thesecond sidelink configuration. Furthermore, the CPU 308 can execute theprogram code 312 to perform all of the above-described actions and stepsor others described herein.

In the context of the embodiments illustrated of FIGS. 16 and 17 anddescribed above, the second sidelink configuration could be generatedbased on a first sidelink configuration provided by the first networknode to the first UE. Furthermore, the first or second sidelinkconfiguration could include an identity of a sidelink logical channelfor the one-to-one sidelink communication, a priority and/or areliability of a sidelink logical channel for the one-to-one sidelinkcommunication, an identity of a sidelink logical channel group for asidelink logical channel for the one-to-one sidelink communication,and/or an identity of a QoS flow for a sidelink logical channel for theone-to-one sidelink communication.

In one embodiment, the second sidelink configuration could betransmitted by a PC5-RRC message. Furthermore, the second UE is servedby the first base station (e.g. gNB) or by a second base station (e.g.gNB).

In one embodiment, the first UE is an initiating UE, and the second UEis a target UE.

Alternatively, as illustrated in FIG. 15C, the UE-1 could transmit aservice request message (e.g. Service Request, a NAS message) to a corenetwork (e.g. V2X Control Function). In the service request message, thecontent could include at least one of the following:

-   An identity of the UE-2;-   An identity of the V2X application;-   An identity of the service provided by the V2X application;-   PC5 5QI of a Qos flow for the V2X application or V2X service; and/or-   PC5 QoS parameters, levels, or profiles of a QoS flow for the V2X    application or V2X service.

With the service request message, the core network could verify the PC55QI of the Qos flow and/or the PC5 QoS parameters, levels, or profilesof the QoS flow with core network (e.g. V2X Control Function). The corenetwork could indicate the base station to provide UE-1 with areconfiguration message. In response to reception of the service requestmessage, the core network could transmit a service accept message (e.g.Service Accept, a NAS message) to UE-1. In one embodiment, the serviceresponse message could be contained or included in the reconfigurationmessage. Alternatively, the service response message could betransmitted to UE-1 via a separate RRC message.

A list of sidelink logical channel could be included in thereconfiguration message, and for each sidelink logical channel thereconfiguration message could include at least one of the following:

-   An identity of a sidelink radio bearer associated with a sidelink    logical channel used for sidelink traffic;-   An identity of the sidelink logical channel;-   A priority of the sidelink logical channel;-   An identity of a sidelink logical channel group (LCG) associated    with the sidelink logical channel; and/or-   An identity of a QoS flow mapped to the sidelink logical channel.

In the service accept message, the content could include:

-   An identity of the sidelink radio bearer associated with the    sidelink logical channel; and/or-   An identity of a QoS flow mapped to the sidelink radio bearer.

Based on the above reconfiguration message and service accept message,UE-1 could create at least a sidelink logical channel for the one-to-onesidelink communication. Furthermore, UE-1 could associate the sidelinklogical channel with a corresponding sidelink LCG. In addition, UE-1could store a mapping of a QoS flow to the corresponding sidelinklogical channel.

Alternatively, as illustrated in FIG. 15D, UE-1 could transmit a servicerequest message (e.g. Service Request, a NAS message) to a core network(e.g. V2X Control Function). In the service request message, the contentcould include at least one of the following:

-   An identity of the UE-2;-   An identity of the V2X application;-   An identity of the service provided by the V2X application;-   PC5 5QI of a Qos flow for the V2X application or V2X service;-   PC5 QoS parameters/levels/profiles of a QoS flow for the V2X    application or V2X service; and/or-   5-tuple (e.g. source IP addresses, destination IP addresses, source    port number, destination port number and protocol ID) of a QoS flow    for the V2X application or V2X service.

With the service request message, the core network could verify the PC55QI of the Qos flow and/or the PC5 QoS parameters/levels/profiles of theQoS flow with core network (e.g. V2X Control Function). The core networkcould indicate the base station to provide UE-1 with a reconfigurationmessage. In response to reception of the service request message, thecore network could transmit a service accept message (e.g. ServiceAccept, a NAS message) to UE-1. In one embodiment, the service responsemessage could be contained or included in the reconfiguration message.Alternatively, the service response message could be transmitted to UE-1via a separate RRC message.

A list of sidelink logical channel could be included in thereconfiguration message, and for each sidelink logical channel, thereconfiguration message could include at least one of the following:

-   An identity of a sidelink radio bearer associated with a sidelink    logical channel used for sidelink traffic;-   An identity of the sidelink logical channel;-   A priority of the sidelink logical channel; and/or-   An identity of a sidelink logical channel group (LCG) associated    with the sidelink logical channel.

In the service accept message, the content could include:

-   An identity of the sidelink radio bearer associated with the    sidelink logical channel; and/or-   A Traffic Flow Template (TFT) associated with the sidelink radio    bearer.

Based on the above reconfiguration message and service accept message,UE-1 could create at least a sidelink logical channel for the one-to-onesidelink communication. Furthermore, UE-1 could associate the sidelinklogical channel with a corresponding sidelink LCG. In addition, UE-1could store the TFT associated with the sidelink logical channel.

V. eV2X Message Transfer (Illustrated in FIG. 18)

In UE-1, sidelink traffic from the V2X application could be availablefor transmission to UE-2. In this situation, UE-1 could transmit asidelink buffer status report to the base station for allocatingsidelink resource for the transmission of the sidelink traffic. A formatof LTE SL BSR (as discussed in 3GPP TS 36.321) could be reused for thesidelink buffer status report.

During the one-to-one SL communication with UE-2, UE-1 may move from thecoverage of a source gNB to the coverage of a target gNB. In thissituation, the source gNB has to handover UE-1 to the target gNB. Tomake sure the target gNB can continue to provide the required sidelinkresources to support the one-to-one SL communication, the source gNBneeds to transfer certain sidelink information related to the one-to-oneSL communication to the target gNB.

For example, the source gNB may transfer at least one of the following:

-   An identity of the UE-2, which may be included in a destination    list;-   An identity of the V2X application;-   An identity of the service provided by the V2X application;-   PC5 5QI of a QoS flow for the V2X application or V2X service,    wherein there is at least one QoS flow; and/or-   PC5 QoS parameters, levels, or profiles of a QoS flow for the V2X    application or V2X service, wherein there is at least one QoS flow.

With the sidelink information from the source gNB, the target gNB coulddetermine at least one sidelink configuration for the one-to-onesidelink communication and provide the sidelink configuration(s) to thesource gNB for being included in a handover command (e.g.RRCConnectionReconfiguration message) sent to UE-1. The sidelinkconfiguration could include at least one of the following:

-   An identity of the UE-2, which may be included in a destination    list;-   An identity of a sidelink logical channel used for sidelink traffic    transmission, wherein there is at least one sidelink logical    channel;-   A priority of the sidelink logical channel;-   An identity of a sidelink logical channel group (LCG) associated    with the sidelink logical channel; and/or-   An identity of a QoS flow mapped to the sidelink logical channel,    wherein there is at least one QoS flow mapped to one the sidelink    logical channel.

Alternatively, the source gNB may just send a sidelink configurationstored in the source gNB for UE-1 to the target gNB for use after thehandover procedure is completed. For example, the source gNB may send amessage to the target gNB, wherein the message includes sidelinkconfiguration associated with a one-to-one SL communication between UE-1and UE-2, and the sidelink configuration could contain at least one ofthe following:

-   An identity of the UE-2, which may be included in a destination    list;-   An identity of a sidelink logical channel used for sidelink traffic    transmission, wherein there is at least one sidelink logical    channel;-   A priority of the sidelink logical channel;-   An identity of a sidelink logical channel group (LCG) associated    with the sidelink logical channel; and/or-   An identity of a QoS flow mapped to the sidelink logical channel,    wherein there is at least one QoS flow mapped to one the sidelink    logical channel.

The message could be a HandoverPreparationInformation sent from thesource gNB to the target gNB. The sidelink information could be used bythe target gNB after the UE-1 is handovered from the source gNB to thetarget gNB. The target gNB may modify the sidelink logical channelconfiguration if necessary, and provide the modified sidelink logicalchannel configuration to UE-1 in the handover command sent to UE-1. Anexample of inter-gNB handover is illustrated in FIG. 19, where theRRCConnectionReconfiguration message with information element“mobilityControlInfo” corresponds to a Handover Command.

FIG. 20 is a flow chart 2000 according to one exemplary embodiment fromthe perspective of a source gNB for handling mobility of a UE with aone-to-one sidelink communication. In step 2005, a source gNB receivessidelink information from the UE. In step 2010, the source gNB sends afirst sidelink configuration to the UE for the one-to-one sidelinkcommunication. In step 2015, the source gNB sends a first message to atarget gNB to prepare a handover for the UE, wherein the messageincludes the sidelink information or the first sidelink configuration.

In one embodiment, the sidelink information could include at least oneof the following: an identity of a second UE, an identity of a V2Xapplication, a service identity for the V2X application, PC5 5QI of aQoS flow for the V2X application or a V2X service, and PC5 QoSparameters, levels, or profiles of a QoS flow for the V2X application orthe V2X service.

Furthermore, the first sidelink configuration could include at least oneof the following: an identity of a second UE, an identity of a sidelinklogical channel used for sidelink traffic transmission, a priority ofthe sidelink logical channel, an identity of a sidelink logical channelgroup (LCG) associated with the sidelink logical channel, and anidentity of a QoS flow mapped to the sidelink logical channel.

In one embodiment, the first message could be aHandoverPreparationInformation. Furthermore, the source gNB couldreceive a handover command from the target gNB. The handover commandcould include a second sidelink configuration and the second sidelinkconfiguration is the same as the first sidelink configuration. Thehandover command could also include a second sidelink configuration andthe second sidelink configuration is different from the first sidelinkconfiguration.

In one embodiment, the source gNB sends a second message to the UE forhandover the UE to the target gNB. The second message could be aRRCConnectionReconfiguration. The RRCConnectionReconfiguration could begenerated according to the handover command. TheRRCConnectionReconfiguration could include an information element“mobilityControlInfo”.

Referring back to FIGS. 3 and 4, in one exemplary embodiment a sourcegNB for handling mobility of a UE with a one-to-one sidelinkcommunication, the device 300 includes a program code 312 stored in thememory 310. The CPU 308 could execute program code 312 to enable thesource gNB (i) to receive sidelink information from the UE, (ii) to senda first sidelink configuration to the UE for the one-to-one sidelinkcommunication, and (iii) to send a first message to a target gNB toprepare a handover for the UE, wherein the message includes the sidelinkinformation or the first sidelink configuration. Furthermore, the CPU308 can execute the program code 312 to perform all of theabove-described actions and steps or others described herein.

FIG. 21 is a flow chart 2100 according to one exemplary embodiment fromthe perspective of an initiating UE (User Equipment) establishing aone-to-one sidelink communication with a target UE. In step 2105, theinitiating UE transmits a first PC5 signaling used for establishing theone-to-one sidelink communication, wherein the first PC5 signalingincludes an identity of the target UE and an identity of a V2X(Vehicle-to-Everything) service.

In one embodiment, the initiating UE could be aware of the presence ofthe target UE via a discovery procedure or a one-to-many sidelinkcommunication. Furthermore, the initiating UE could be aware of thepresence of the target UE via reception of one or more V2X messages fromthe target UE. The first PC5 signaling could include an identity of aV2X application offering the V2X service, an identity of the initiatingUE, and/or requested PC5 5QI, QoS (Quality of Service) parameter(s) orQoS profile(s) of a PC5 QoS flow for the V2X application or the V2Xservice.

In one embodiment, the first PC5 signaling could be transmitted to abroadcast address associated with the V2X service or the V2Xapplication. The first PC5 signaling could be a Direct CommunicationRequest message.

In one embodiment, the initiating UE could receive a second PC5signaling from the target UE, wherein the second PC5 signaling is usedto complete establishment of the one-to-one sidelink communication. Thesecond PC5 signaling could include accepted PC5 5QI, QoS parameter(s) orQoS profile(s) of a PC5 QoS flow for the V2X application or the V2Xservice. The second PC5 signaling could be a Direct Communication Acceptmessage.

Referring back to FIGS. 3 and 4, in one exemplary embodiment of aninitiating UE establishing a one-to-one sidelink communication with atarget UE, the device 300 includes a program code 312 stored in thememory 310. The CPU 308 could execute program code 312 to enable theinitiating UE to transmit a first PC5 signaling used for establishingthe one-to-one sidelink communication, wherein the first PC5 signalingincludes an identity of the target UE and an identity of a V2X(Vehicle-to-Everything) service. Furthermore, the CPU 308 can executethe program code 312 to perform all of the above-described actions andsteps or others described herein.

Various aspects of the disclosure have been described above. It shouldbe apparent that the teachings herein could be embodied in a widevariety of forms and that any specific structure, function, or bothbeing disclosed herein is merely representative. Based on the teachingsherein one skilled in the art should appreciate that an aspect disclosedherein could be implemented independently of any other aspects and thattwo or more of these aspects could be combined in various ways. Forexample, an apparatus could be implemented or a method could bepracticed using any number of the aspects set forth herein. In addition,such an apparatus could be implemented or such a method could bepracticed using other structure, functionality, or structure andfunctionality in addition to or other than one or more of the aspectsset forth herein. As an example of some of the above concepts, in someaspects concurrent channels could be established based on pulserepetition frequencies. In some aspects concurrent channels could beestablished based on pulse position or offsets. In some aspectsconcurrent channels could be established based on time hoppingsequences. In some aspects concurrent channels could be establishedbased on pulse repetition frequencies, pulse positions or offsets, andtime hopping sequences.

Those of skill in the art would understand that information and signalsmay be represented using any of a variety of different technologies andtechniques. For example, data, instructions, commands, information,signals, bits, symbols, and chips that may be referenced throughout theabove description may be represented by voltages, currents,electromagnetic waves, magnetic fields or particles, optical fields orparticles, or any combination thereof.

Those of skill would further appreciate that the various illustrativelogical blocks, modules, processors, means, circuits, and algorithmsteps described in connection with the aspects disclosed herein may beimplemented as electronic hardware (e.g., a digital implementation, ananalog implementation, or a combination of the two, which may bedesigned using source coding or some other technique), various forms ofprogram or design code incorporating instructions (which may be referredto herein, for convenience, as “software” or a “software module”), orcombinations of both. To clearly illustrate this interchangeability ofhardware and software, various illustrative components, blocks, modules,circuits, and steps have been described above generally in terms oftheir functionality. Whether such functionality is implemented ashardware or software depends upon the particular application and designconstraints imposed on the overall system. Skilled artisans mayimplement the described functionality in varying ways for eachparticular application, but such implementation decisions should not beinterpreted as causing a departure from the scope of the presentdisclosure.

In addition, the various illustrative logical blocks, modules, andcircuits described in connection with the aspects disclosed herein maybe implemented within or performed by an integrated circuit (“IC”), anaccess terminal, or an access point. The IC may comprise a generalpurpose processor, a digital signal processor (DSP), an applicationspecific integrated circuit (ASIC), a field programmable gate array(FPGA) or other programmable logic device, discrete gate or transistorlogic, discrete hardware components, electrical components, opticalcomponents, mechanical components, or any combination thereof designedto perform the functions described herein, and may execute codes orinstructions that reside within the IC, outside of the IC, or both. Ageneral purpose processor may be a microprocessor, but in thealternative, the processor may be any conventional processor,controller, microcontroller, or state machine. A processor may also beimplemented as a combination of computing devices, e.g., a combinationof a DSP and a microprocessor, a plurality of microprocessors, one ormore microprocessors in conjunction with a DSP core, or any other suchconfiguration.

It is understood that any specific order or hierarchy of steps in anydisclosed process is an example of a sample approach. Based upon designpreferences, it is understood that the specific order or hierarchy ofsteps in the processes may be rearranged while remaining within thescope of the present disclosure. The accompanying method claims presentelements of the various steps in a sample order, and are not meant to belimited to the specific order or hierarchy presented.

The steps of a method or algorithm described in connection with theaspects disclosed herein may be embodied directly in hardware, in asoftware module executed by a processor, or in a combination of the two.A software module (e.g., including executable instructions and relateddata) and other data may reside in a data memory such as RAM memory,flash memory, ROM memory, EPROM memory, EEPROM memory, registers, a harddisk, a removable disk, a CD-ROM, or any other form of computer-readablestorage medium known in the art. A sample storage medium may be coupledto a machine such as, for example, a computer/processor (which may bereferred to herein, for convenience, as a “processor”) such theprocessor can read information (e.g., code) from and write informationto the storage medium. A sample storage medium may be integral to theprocessor. The processor and the storage medium may reside in an ASIC.The ASIC may reside in user equipment. In the alternative, the processorand the storage medium may reside as discrete components in userequipment. Moreover, in some aspects any suitable computer-programproduct may comprise a computer-readable medium comprising codesrelating to one or more of the aspects of the disclosure. In someaspects a computer program product may comprise packaging materials.

While the invention has been described in connection with variousaspects, it will be understood that the invention is capable of furthermodifications. This application is intended to cover any variations,uses or adaptation of the invention following, in general, theprinciples of the invention, and including such departures from thepresent disclosure as come within the known and customary practicewithin the art to which the invention pertains.

1. A method for an initiating UE (User Equipment) to establish a unicastlink with a target UE, comprising: transmitting a first PC5 signaling toa broadcast address associated with a V2X (Vehicle-to-Everything)service or a V2X application offering the V2X service, wherein the firstPC5 signaling includes an application layer identity of the target UE;receiving a second PC5 signaling from the target UE; and transmittingone or more V2X messages to the target UE via the unicast link, whereinthe unicast link is associated with the first PC5 signaling and thesecond PC5 signaling.
 2. The method of claim 1, wherein the initiatingUE is aware of the presence of the target UE via a discovery procedureor a one-to-many sidelink communication.
 3. The method of claim 1,wherein the first PC5 signaling includes an identity of a V2Xapplication offering a V2X service.
 4. The method of claim 1, whereinthe first PC5 signaling includes an application layer identity of theinitiating UE.
 5. The method of claim 1, wherein the first PC5 signalingincludes requested PC5 5QI, QoS (Quality of Service) parameter(s) or QoSprofile(s) of a PC5 QoS flow for a V2X application offering a V2Xservice or the V2X service.
 6. The method of claim 1, wherein the secondPC5 signaling includes accepted PC5 5QI for a V2X application offering aV2X service or the V2X service.
 7. The method of claim 1, wherein thefirst PC5 signaling is a Direct Communication Request message.
 8. Themethod of claim 1, wherein the second PC5 signaling includes QoS(Quality of Service) parameter(s) for a V2X application offering a V2Xservice or the V2X service.
 9. The method of claim 1, wherein the secondPC5 signaling includes QoS (Quality of Service) profile(s) of a PC5 QoSflow for a V2X application offering the V2X service or the V2X service.10. The method of claim 1, wherein the second PC5 signaling is a DirectCommunication Accept message.
 11. An initiating communication device,comprising: a control circuit; a processor installed in the controlcircuit; and a memory installed in the control circuit and operativelycoupled to the processor; wherein the processor is configured to executea program code stored in the memory to: transmit a first PC5 signalingto a broadcast address associated with a V2X (Vehicle-to-Everything)service or a V2X application offering the V2X service, wherein the firstPC5 signaling includes an application layer identity of a targetcommunication device; receive a second PC5 signaling from the targetcommunication device; and transmit one or more V2X messages to thetarget communication device via a unicast link associated with the firstPC5 signaling and the second PC5 signaling.
 12. The initiatingcommunication device of claim 11, wherein the initiating communicationdevice is aware of the presence of the target communication device via adiscovery procedure or a one-to-many sidelink communication.
 13. Theinitiating communication device of claim 11, wherein the first PC5signaling includes an identity of a V2X application offering a V2Xservice.
 14. The initiating communication device of claim 11, whereinthe first PC5 signaling includes an application layer identity of theinitiating communication device.
 15. The initiating communication deviceof claim 11, wherein the first PC5 signaling includes requested PC5 5QI,QoS (Quality of Service) parameter(s) or QoS profile(s) of a PC5 QoSflow for a V2X application offering a V2X service or the V2X service.16. The initiating communication device of claim 11, wherein the secondPC5 signaling includes accepted PC5 5QI for a V2X application offering aV2X service or the V2X service.
 17. The initiating communication deviceof claim 11, wherein the first PC5 signaling is a Direct CommunicationRequest message.
 18. The initiating communication device of claim 11,wherein the second PC5 signaling includes QoS (Quality of Service)parameter(s) for a V2X application offering a V2X service or the V2Xservice.
 19. The initiating communication device of claim 11, whereinthe second PC5 signaling includes QoS (Quality of Service) profile(s) ofa PC5 QoS flow for a V2X application offering a V2X service or the V2Xservice.
 20. The initiating communication device of claim 11, whereinthe second PC5 signaling is a Direct Communication Accept message.